Homogeneous polymerization of vinylidene compounds with an alpha, alpha-dialkylarylmethyl hydroperoxide and a heavy metal compound as catalyst



Patented Sept. 30, 1952 HOMOGENEOUS POLYMERIZATION OF VINYLIDENE COMPOUNDS WITH JAN a-,ar--DIALKYLARYLMETHYL "HYDRO- "PEROXDJEYAND A HEAVY METAL COM- ;POUND AS CATALYST Charles Gould, =Wilmington, Del., 'assignor'to Hercules Powder Company, Wilmington, DeL, a corporation :of Delaware jiNoflDrawing.

This invention relates to-an'improvedprocess (for the homogeneous polymerization of unsaturated compounds and more particularly to an improved 'process of homogeneously polymerizing zvinyl, :vinylidene, and vinylene compounds.

':It is well known that i the homogeneous 1 polymerization of vinyl-type compounds may 'be -ac 'celeratedc by means of heat, actinic light, or a catalyst such as the organic peroxides. Of-these accelerators, the peroxidi'ccatalysts have 'been 'the most widely employed but difiiculty is frequently encountered .in'o'btaining a high yield of the ;.polymer in a reasonable length of time. 'In additi'ommany of ithe peroxide catalysts tend-to discolor the .polymer and to produce polymers 'with :lower average molecular weights.

.Now in accordance with this invention it has been found that the homogeneous polymerization of "monomeric compounds containing the CH2=C group and which tare capable of being polymerized by a peroxide catalyst: may be carried out vtofiadvantagel'in:the :presence of an a i- .dialkylarylmethyl :hydroperoxide :and a heavy metal :acetylacetonate. Thezincorporation vofxthe acetylacetonate not onlyimakes possible a 'more completepolymerizationibut also zpermits the :use of lower temperaturesrfor the reaction. In addition, air 'does 'not have to ':be excluded 'from the vpolymerization reaction since the presence \of oxygen actually improves .the ,.polymerization when initiated by the combination of ethere dialkylarylmethyl hy'droperoxide and heavy metal. zacetylacetonate.

. The following examples sareiillustrativezof \the process :of homogeneous polymerization in" F130- cordance with thisinvention. All parts and-percentages given in the examples represent parts andy-pereentages by weight.

Example 1 Two glass polymerization vessels were charged with a solution of 0.9 part of ferric acetylacetonate-and -2. 7-parts of a 46% solution of apt-dimethylbenzyl hydroperoxide in cumene, in 200 parts of freshly distilled methyl isopropenyl ketone. .All of the air was evacuated from one of the vessels before closing and the other vessel was vclosed without removing the air. The polymerization reaction was carried out by heating each vessel to.50 C. for a period of one week In each case the polymer obtained was soluble in methyl ethyl ketone and insoluble in methanol. In the absence of air a 49% yield of a soft polymer was obtained whereas in the presence of air there was obtained a 100% yield of a polymer which'hadahardness of 30 and cold flow of 6 as determined by a Barcol Impressor.

this invention is carried out by the bulk or solu- Application December 24, 1948, 'Serial No. 67,243

'9 claims. (01. 260-63) v I Example? Duplicatingthe procedure of Example '1, methyl methacrylate was polymerized iin'the presence of a,a'-dimethylbenzyl"hydroperoxide andferric acetylacetonate "in the presence ,of air and in the absence .of .air. "The polymers were soluble .in methyl ethyl ketone and insoluble in methanol. The yield and ,the'ihardness and cold flow as determinedby a'Barcol Impressor' are tabulated-below.

Percent Polymerization in Yield Hardness Cold Flow ,Polymer Absence of air 91 25 10 Presence ofair -94 35 :5

Example 3 The procedure of Example l'was repeated using styrene asthe'monomericmaterial. A 95% "yield wasobtainedboth with'and' without air, but'the polymer "formed 'intheipresence of air was more completely "cured, having a hardness of 15 "and coldi'fiow df 3 as 'comparedwith a hardness "of 5 and cold flowof '7 "forthepolymer-"prepared in the absence of 'air.

' Example 4 "Two 'glass' polymerizationvessels were charged with parts of powdered 'hydroabietyl fumarate,-2.0-=parts of a-dimethylbenzylhydroperoxide, 0.2 part of ferric"acetylacetonate, 'and25 parts of isobutylene. A slightexcessof lisobutyl- 'ene'wa-s'added to-one the vessels and then permitted to-boil off in order to sweep 'all -air out ofthe free-space beforesealing. The-'otheryes- 'sel was closed without removing the air from the free space. Both vessels and their-contents Were-then heated to 65 'C. and "the extent of polymerization was determined by removing an aliquot from :the -vessel :at the end :of 7 and '24 hours. The results are setiorthbelow, the per cent conversion indicated being "the per cent of 'hy'droabietyl fumarate converted rto the= copolymer.

The polymerization process in accordance (with peroxides.

tion of initiators results in the production of polymers having excellent properties, which are.

monomers, and preferably is from about 0.1% to about 3 The addition of a heavy metal acetylacetonate to the polymerization system in which an a,a-dieven further improved by the presence of oxygen 7 during the polymerization reaction.

The a,a-dialkylarylmethyl hydroperoxides used as the catalysts in the process of this invention have the following structural formula R1 OOH Rz Ar where R1 and R2 represent alkyl groups and Ar represents a substituent selected from the group consisting of aryl and alkaryl groups. Exemplary of such hydroperoxides are apdimethylbenzyl, a,a-dimethyl-p-isopropylbenzyl, a,a-dimethyl-pmethylbenzyl, and a,a-ethylmethylbenzyl hydro- These compounds may also be named as a'ryl(dialkyl) methyl hydroperoxides.

The a,-dialkylarylmethy1 hydroperoxides may be prepared by the oxidation of alkyl-substituted aromatic organic compounds having the ,structural formula compounds having the above structural formula by passing an oxygen-containing gas through the compounds at a temperature between about 25 and about 95 C. in the presence of an aqueous alkali. The concentration of the aqueous alkali may be between about 1 and about 35% although it is preferable to use concentrations of about 2 to about 8%. Vigorous agitation is desirable during the oxidation reaction.

As illustrative of the alkyl-substituted aromatic organic compounds which may be oxidized, pcym-ene, cumene, diisopropyl benzene, and secbutylbenzene may be mentioned. These compounds lead to a -dimethyl-p-methylbenzyl, a,rz

dimethylbenzyl, a,a-dimethyl-p-isopropylbenzyl, and a,a-ethylmethylbenzyl hydroperoxides, respectively. The aryl and alkaryl groups need not be derived from benzene, as is the case in the aforementioned compounds, for compounds containing aromatic nuclei derived from naphthalene, anthracene, phenanthrene, and the like also are operable when dissolved in a suitable solvent during the oxidation. The aryl group may be substituted with alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, secondary butyl, tertiary butyl and the like, the same alkyl groups also being representative of R1 and R2 in the structural formula. R1 and R2 may be either the same or different.

The amount of hydroperoxide which may be used in accordance with this invention may be from about 0.001% to about 5.0% based on the polymerization.

. alkylarylmethyl hydroperoxide is used as catalyst is advantageous in that more complete polymeri- "zation is obtained and consequently a harder polymer is formed. Among the heavy metal acetylacetonates which may be used are the acetylacetonates of iron (either ferrous or ferric), cobalt, nickel, copper, silver, zinc, cadmium, mercury, chromium, manganese, or molybdenum. The heavy metal acetylacetonate should be used in an amount such as will provide from about 0.001% to about 0.35% and preferably about 0.01% to about 0.2% of the heavy metal based on the weight of monomers used and accordingly the amount of metal acetylacetonat-e will vary from about 0.01% to about 2.5% and preferably about 0.05% to about 1.0%.

As may be seen from the foregoing examples, it is not necessary to exclude air from the polymerization system when the polymerization is carried out by the process in accordance with this invention. In fact, the presence of oxygen actually improves theaccelerating effect of the metal compound, an excellent cure being obtained under the same conditions which yielded an undercured polymer in the absence of the oxygen. This is most unusual since the presence of air usually has a deleterious effect on polymerizations. Thus, the use of the combination of a,a-dlalkylarylmethyl hydroperoxide and metal acetylaoetonate obviates the necessity for rigorously excluding air and thus it is possible to carry out the polymerization reaction by heating or refluxing the reactants in an open reaction vessel if desired. It'also makes it possible to carry out the polymerization while exposed to air as is necessary in such applications as in coatings, or in continuous casting or laminating of thin sheets. The

oxygen may be present as free oxygen, or as an oxygen-containing gas such as air or mixtures of oxygen with an inert gas such as nitrogen.

The homogeneous polymerization in accordance with this inventionmay be carried out by either bulk or solution polymerization under the conditions well known in the art for homogeneous The temperature of the polymerization reaction may vary from about 25 to about 100 C. and preferably is from about 50 to about 80 C. The examples have illustrated the process of carrying out the homogeneous polymerization in accordance with this invention by means of bulk polymerization. The process is equally applicable, however, to solution polymerization; i. e., polymerization in a solvent such as benzene, toluene, xylene, hexane, acetone, and

the like.

Compounds which may be advantageously polymerized in accordance with this invention include any vinyl or vinylidene compounds; i. e., compounds containing the CH2=C group, which are capable of being polymerized by a peroxide catalyst. Monomers which may be so polymerized are the conjugated butadienes such as butadiene, isoprene, dimethyl butadiene, chloroprene, etc., and other compounds containing the vinyl group such as styrene,' acrylonitrile, acrylic acid esters such as methyl acrylate, etc., methacrylic acid esters such as methyl methacrylate, methyl vinyl ketone, methyl isopropenyl ketone, vinyl pyridine, various vinyl ethers and esters, and other monomers which form addition polymers, as well as monomer mixtures of two or more of these monomers. In addition to the monomers containing the CH2=C group which are capable of being polymerized by a peroxide catalyst are those monomers containing such a group which in combination with another unsaturated monomer provide a combination which is capable of polymerization with a peroxide catalyst as, for example, the isobutylene-hydroabietyl fumarate combination shown in Example 4.

The polymerization processes of this invention are advantageous in that they allow the use of polymerization temperatures which are far below the thermal decomposition temperatures of the hydroperoxide and at the same time yield a completely cured polymer. A faster polymerization rate at a given temperature is obtained and it is possible to carry out bulk polymerization without rigorously excluding air and thus can be used advantageously in such applications as casting vinyl resins and in contact pressure laminating with polyester-type resins.

What I claim and desire to protect by Letters Patent is:

1. The process which comprises homogeneously polymerizing a monomeric compound containing the CH2=C group and which is capable'of being polymerized by a peroxide catalyst, in the presence of a catalyst comprising an a,a-dialkyl arylmethyl hydroperoxide in which each alkyl group contains not more than 4 carbon atoms and a heavy metal acetylacetonate.

2. The process which comprises homogeneously polymerizing a monomeric compound containing the CH2=C group and which is capable of being polymerized by a peroxide catalyst, in the presence of a catalyst comprising an a,a-dialkylarylmethyl hydroperoxide in which each alkyl group contains not more than 4 carbon atoms, a heavy metal acetylacetonate, and oxygen.

3. The process which comprises homogeneously polymerizing a monomeric compound containing the CH2=C group and which is capable of being polymerized by a peroxide catalyst in the presence of a catalyst comprising a,a-dimethylbenzyl hydroperoxide and iron acetylacetonate.

4. The process which comprises homogeneously polymerizing a monomeric compound containing the CH2=C group and which is capable of being polymerized by a peroxide catalyst in the presence of a catalyst comprising a,a-dimethylbenzyl hydroperoxide, iron acetylacetonate, and oxygen.

5. The process which comprises homogeneously polymerizing styrene in the presence of a catalyst comprising a,a-dimethylbenzyl hydroperoxide, ferric acetylace'tonate, and. oxygen.

6. The process which comprises homogeneously polymerizing methyl methacrylate in the presence of a catalyst comprising a,a-dimethylbenzy1 hydroperoxide, ferric acetylacetonate, and oxygen.

'7. The processwhich comprises homogeneously polymerizing methyl isopropenyl ketone in the presence of a catalyst comprising a,a-dimethylbenzyl hydroperoxide, ferric acetylacetonate, and oxygen.

8. The process which comprises homogeneously copolymerizing a monomeric compound containing the CH2=C group with an ethylenic unsaturated monomeric compound copolymerizable with the vinylidene compound in the presence of a peroxide catalyst, in the presence of a catalyst comprising an a,a-dialkylarylmethyl hydroperoxide in which each alkyl group contains not more than 4 carbon atoms and a heavy metal acetylacetonate.

9. The process which comprises homogeneously copolymerizing a monomeric compound containing the CH2=C group with an ethylenic unsaturated monomeric compound copolymerizable with the vinylidene compound in the presence of a peroxide catalyst, in the presence of a catalyst comprising an a,v.-dialkylarylmethy1 hydroperoxide in which each alkyl group contains not more than 4 carbon atoms, a heavy metal acetylacetonate, and oxygen.

CHARLES W. GOULD.

REFERENCES CITED The following references are of record in the file of this patent: 1

UNITED STATES PATENTS Number Name Date 2,380,474 Stewart July 31, 1945 2,395,523 Vaughan et a1 Feb. 26, 1946 FOREIGN PATENTS Number Country Date 582,899 Great Britain Dec. 2, 1946 610,293 Great Britain Oct. 13, 1948 

1. THE PROCESS WHICH COMPRISES HOMOGENEOUSLY POLYMERIZING A MONOMERIC COMPOUND CONTAINING THE CH2=C< GROUP AND WHICH IS CAPABLE OF BEING POLYMERIZED BY THE PEROXIDE CATALYST, IN THE PRESENCE OF A CATALYST COMPRISING AN A,A-DIALKYLARYLMETHYL HYDROPEROXIDE IN WHICH EACH ALKYL GROUP CONTAINS NOT MORE THAN 4 CARBON ATOMS AND A HEAVY METAL ACETYLACETONATE. 